In general, a hydraulic excavator as a construction machine includes a lower track structure, an upper swing structure disposed swingably on the lower track structure, and an articulated work implement (work device) including a boom, an arm, and a bucket, which is disposed elevatably on the upper swing structure. A hydraulic drive system of this hydraulic excavator includes a prime mover (specifically, for example, an engine or a main electric drive motor), a main pump and a pilot pump which are driven by the prime mover, a plurality of directional control valves for controlling respective flows of hydraulic fluid from the main pump to a plurality of hydraulic actuators (specifically, for example, a boom hydraulic cylinder, an arm hydraulic cylinder, and a bucket hydraulic cylinder), and a plurality of operating devices for directing operations of the multiple hydraulic actuators. The operating device is, for example, a hydraulic pilot type including a pilot valve that uses a delivery pressure of the pilot pump as a source pressure to thereby generate a pilot pressure reduced according to an operation of a control lever. The pilot pressure thus generated is then output to a pressure receiving portion of the directional control valve to thereby change the position of the directional control valve.
The hydraulic excavator includes an air-cooled heat exchanger (specifically, for example, an oil cooler for cooling hydraulic fluid and, in a hydraulic excavator having an engine as the prime mover, for example, a radiator for cooling engine coolant) and a cooling fan for generating cooling air for the heat exchanger. A known hydraulic excavator includes a fan electric drive device, driven by electric power of a battery, for rotating a cooling fan independently of a prime mover (see, for example, patent document 1). This fan electric drive device includes, for example, a fan electric drive motor for rotating a cooling fan. Or, the fan electric drive device includes, for example, a fan hydraulic motor for rotating a cooling fan, a fan pump for generating hydraulic fluid to be supplied to the fan hydraulic motor, and a fan electric drive motor for driving the fan pump.
Other known hydraulic excavators include a lock lever and locking means provided for preventing the operating device from being erroneously operated (see, for example, patent documents 2 and 3). Specifically, the lock lever is disposed at a boarding-alighting port and placed into an unlocked position (specifically, a lowered position of impeding boarding and alighting of an operator) and a locked position (specifically, a raised position of permitting boarding and alighting of the operator). The locking means makes an operation of the operating device ineffective or the operating device inoperative when the lock lever is placed in the locked position.
The hydraulic excavator disclosed in patent document 2 includes, as locking means for making an operation of a work operating device ineffective when a lock lever is placed in a locked position, a lock switch (stop switch) and a solenoid lock valve (cutoff valve). The lock switch opens and closes according as the lock lever is operated. The lock valve is disposed at a hydraulic line between a pilot pump and the operating device and operated by a signal from the lock switch. When, for example, the lock lever is placed in an unlocked position, the lock switch closes to thereby operate the lock valve, providing communication between the pilot pump and the operating device. When, for example, the lock lever is placed in the locked position, on the other hand, the lock switch opens to thereby make the lock valve inoperative, which interrupts the communication between the pilot pump and the operating device. As a result, no pilot pressure is generated even when the control lever of the work operating device is operated, so that a hydraulic actuator is inoperative.
The hydraulic excavator further includes, as locking means for making a travel operating device inoperative when the lock lever is placed in the locked position, a lever engaging portion connected to the lock lever. When, for example, the lock lever is placed in the locked position, the lever engaging portion restricts a control lever of the travel operating device. This makes the control lever inoperative, so that a hydraulic actuator is inoperative.
The electrically driven hydraulic excavator disclosed in patent document 3 (specifically, a hydraulic excavator having a main electric drive motor as the prime mover) includes, as locking means, a control unit that stops the main electric drive motor when a lock lever is placed in a locked position.